As it is known, washing machines are internally provided with a rotary drum that is designed to be filled with dirty laundry and is exactly housed inside a basically cylindrical oscillating assembly.
In particular, such a drum is provided on the bottom wall with a shaft that, after crossing the bottom wall of the oscillating assembly that contains it, is connected to an electrical motor that drives it into rotation.
Considering that the drum of washing machines is subjected to quite high rotational speed (especially during the spin drier cycle), it appears evident that the rotations generate significant mechanical stress for the oscillating assembly that contains the drum.
In order to prevent the said stress from damaging the structure, the oscillating assembly is mounted inside the case of the appliance with the interposition of suitable elastic connection elements that act as shock absorbers.
Because of the high intensity of the stress, the said elastic elements must be adjusted loosely, in such a way to allow the oscillating assembly to be displaced, including significantly, inside the case.
Although the fact that the oscillating assembly is mounted on the said elastic elements preserves the structural integrity of the oscillating assembly during the operation of the washing machine, it must be noted that such a solution causes a problem during the packing and transport operations of the appliance.
During the said operations, the oscillating assembly of a washing machine is exposed to such strong shaking that it can hit the internal walls of the case of the appliance, causing serious damage.
In order to prevent this problem, when the assembly of the washing machine has been completed, a common practice consists in mounting inside the washing machine some devices designed to stop the oscillations of the oscillating assembly, which are able to neutralise the presence of the said shock absorbers.
Of course, the said devices are designed to operate only during the packing and transport operations of the appliance, and are immediately removed before the appliance is put in operation, when the oscillating assembly is subjected again to the shock absorbing action of the elastic elements fixed to the cabinet.
An especially popular type of the said devices is represented by a spacer that practically consists in a cylindrical pin made of rigid plastic material and provided with enlarged head.
Such a spacer is crossed by an axial hole with circular section, in which a fixing screw is inserted, with suitable length to come out shortly from the front end of the hole.
Such a spacer must be horizontally inserted inside one of the holes provided on the back wall of the cabinet of a washing machine, until the enlarged head touches the external side of the back wall, in such a way to prevent the uncontrolled insertion of the entire spacer inside the appliance.
Following to the said insertion, the tip of the screw inserted in the spacer penetrates inside a hole obtained in corresponding position in the oscillating assembly contained inside the cabinet.
Then the screw of the spacer is screwed, in such a way that the front end of the spacer energetically interfered against the surface of the oscillating assembly and the enlarged head energetically adheres against the external side of the back wall of the cabinet of the appliance.
Evidently, such a spacer obtains a rigid connection between the oscillating assembly and the cabinet of the appliance.
It must be noted that, in order to make the said spacers effective, each of them is provided with an insert that is able to be elastically compressed, causing a bulge on the internal wall of the cabinet, when the screw is engaged in the hole obtained on the oscillating assembly to be stopped.
Generally, the elastically deformable insert consists in a rubber collar designed to be inserted along the same screw that crosses the cylindrical rigid body of a spacer.
In many instances the collar is provided with an enlarged head and for this reason it is designed to be mounted upstream the said cylindrical rigid body, in such a way that the enlarged head interferes against the external side of the back wall of the cabinet during the installation of the spacer.
In any case it must be noted that, when the spacer is screwed against the back side of the oscillating assembly, the elastic insert is subjected to a compression load that causes circumferential expansion, thus strengthening the connection between the oscillating assembly of a washing machine and the corresponding cabinet.
In fact, also when the oscillating assembly is subjected to stress that tends to push it against the back wall of the cabinet, the spacer is no longer free to move backwards and come out of the insertion hole, the said backward movement being prevented by the annular bulge suffered by the said insert under compression.
The said spacers are classified by the experts of the art as “bi-components”, because that they are formed of two components: a bearing rigid element and an insert made of elastically expandable material under compression.
A “bi-component” spacer of this type is illustrated in patent WO 2006/129176.
Other models of spacers are known, being characterised in that they have a monolithic structure that comprises a cylindrical stem and an enlarged circular head, both crossed by an axial conduit for the screw used to fix the spacer between the oscillating assembly and the back wall of the cabinet of the washing machine.
In order to provide secure coupling between the circular head and the back wall of the cabinet, the head is provided with an annular groove, whereas the back wall of the cabinet is provided with a “keyhole”-type hole, with “eye” having the same diameter as the cylindrical stem of the spacer, and the width of the slot that starts from the said “eye” is the same as the diameter of the said annular grove.
This means that, once the cylindrical stem of the spacer has been inserted into the eye of the “keyhole-type” hole, the installer must slide the spacer laterally, in parallel direction, in order to insert the edges of the slot into the annular groove of the head of the spacer, which is interlocked in the back wall of the cabinet.
A spacer of this second type is disclosed in patent EP 0916760.
Although this second type of spacer is preferred to the first one because of its monolithic structure, which is simple and inexpensive to make, it is impaired in that it requires the drilling of “keyhole”-type holes on the back wall of the cabinet.